In the semiconductor field, integrated circuits are manufactured from large pieces of semiconductor material commonly known as wafers. The wafers have deposited on them various layers of conducting and non-conducting material. Each of these layers are separately deposited on the wafer, as it is built up in a step-by-step process. The layers can be applied to the wafer using any one of several methods which are well known in the art.
One of these well-known deposition methods involves the use of a sputter machine. A sputter machine typically deposits a conductive material, such as aluminum, onto the wafer. In the sputter process, a sputter target containing a layer of conductive material is mounted into a cavity in the sputter machine. Several wafers are then placed beneath the sputter target. The wafers and the metal are oppositely charged, and the metal is deposited onto the wafers using an electrical process.
The amount of conductive material which is deposited onto the wafer is carefully controlled. This is because it is necessary to build up layers of uniform thickness on the wafer. Any impurities which may be present during the sputter process can become deposited onto the wafers. These impurities are also undesirable as they eventually lead to decreased manufacturing yields in the sputter process. These decreased yields directly increase the cost of manufacturing the semiconductors.
In order to eliminate as many impurities as possible, the sputter process is carried out in a vacuum. This does not, however, require that the entire sputter machine be placed within a vacuum. Instead, the cavity within the sputter machine is evacuated during the sputter process. Therefore, when the sputter target is mounted onto the sputter machine, there needs to be an airtight seal between the target and the machine. Without this seal, air would quickly leak into the cavity, thus allowing impurities to be introduced to the sputter process.
The sputter process transfers the layer of conductive material from the sputter target to the wafer. As a result, the conductive material becomes depleted over time. It is therefore necessary to periodically replace the sputter target with a target containing a new layer of conductive material. In prior art sputter devices, there was no way of testing a target prior to its being mounted on the machine to insure that there would be an effective seal between the target and the machine. Often, a new target would be placed on the machine and the vacuum cavity would be evacuated before it was discovered that there was a leak in the seal. Thus, additional time would be necessary to replace the defective target and again draw the air out of the cavity.
All of the time spent while the new target is being placed into the sputter machine is undesirable because the manufacturing process must be shut down. This downtime leads directly to increased production costs for the semiconductor devices.